Question

Consider the following code.

class MainWindow
{
    // ...
    Phonon::MediaObject media;
    Phonon::AudioOutput audio_output;
};

MainWindow::MainWindow() : audio_output(MusicCategory)
{
    //...

    QList<EffectDescription> effects =
                          BackendCapabilities::availableAudioEffects();

    media.setCurrentSource(MediaSource("../test.wma"));
    Path path = createPath(&media, &audio_output);
    Q_ASSERT(path.isValid());

    if (!effects.isEmpty())
    {
        path.insertEffect(effects[2]);
    }

    media.play();

    qDebug() << "Playing...";
}

After the constructor returns, path and effects will be destroyed. I’ve noticed that the media continues to play even with the effect applied (effects[2]).

I think I missed something. Even if path and effects are destroyed, how does media continue to play?

Answer 1

As The Path::~Path documentation says:

Destroys this reference to the Path. If the path was valid the connection is not broken as both the source and the sink MediaNodes still keep a reference to the Path.

That means that paths are more like handles than following RAII principles.
You have to explicitely call disconnect() to destroy the connection.